1. Field of the Invention
The invention relates to a method for transceiving data over guard sub-carriers in multi-band Orthogonal Frequency Division Multiple Access (OFDMA) systems.
2. Description of the Related Art
Orthogonal frequency division multiplexing (OFDM) is an efficient modulation scheme for signal transmission over frequency-selective channels. In OFDM, a wide bandwidth is divided into multiple narrow-band sub-carriers, which are arranged to be orthogonal with each other. The signals modulated on the sub-carriers are transmitted in parallel. Orthogonal frequency division multiple access (OFDMA) is one way using the basic format of OFDM to support multiple access for multiple subscribers. In OFDMA, multiple subscribers simultaneously use different sub-carriers, in a fashion similar to frequency division multiple access (FDMA).
In the recent years, OFDMA has been used as an efficient multiple access scheme to perform high speed wireless transmission over frequency selective channels with high spectral efficiency. Multi-band OFDMA is expected to be one of the essential technologies for fourth generation (4G) mobile cellular systems. 4G mobile cellular systems require, for example, up to 1 Gbps peak transmission rate and extended data transmission bandwidth.
Multi-band OFDMA utilizes multiple Radio Frequency (RF) carriers to obtain extended data transmission bandwidth. FIG. 1 is a spectrogram illustrating an exemplary example of extended data transmission bandwidth by using four contiguous RF carrier bands (labeled by Band #1, Band #2, Band #3 and Band #4). Each RF carrier band is centralized with an RF carrier frequency, and comprises a predetermined amount of sub-carriers. For example, the amount of sub-carriers in each RF carrier band may be 1024 (corresponds to 1024 points of Inverse Fast Fourier Transform (IFFT)), and the bandwidth of the RF carrier band may be bound to about 10 MHz. In order to further improve the spectral efficiency of the multi-band OFDMA system, a novel data transceiving method with increased transmission rate is highly required.